1. Field of the Invention
This invention relates to a method of producing branched chain esters as for example methyl-2,2,3,3-tetramethylbutyrate, from methanol and carbon monoxide.
2. Description of the Prior Art
Previous efforts to convert methanol to higher carbon number molecules have led to hydrocarbons rather than esters. Even this prior experimental work with methanol conversion to hydrocarbons may be characterized as largely academic or substantially uneconomic in present terms. For example, as early as 1878, LeBel and Green (Compt. Rend. Vol. 87, p. 260) produced alkyl hydrocarbons by contacting methanol with zinc chloride at elevated temperatures. More recently, Grosse and Snyder describe and claim a process in U.S. Pat. No. 2,492,984 wherein a mixture consisting essentially of a specified metal halide and at least one compound selected from the group consisting of methanol and dimethyl ether is subjected to conversion conditions, including a temperature of 250.degree. C. to 650.degree. C., to form substantial amounts of recoverable hydrocarbons having at least four carbon atoms. The examples of the patent employ a zinc chloride catalyst, and the specification mentions that higher atomic weight halides of metals such as zinc, cadmium, thorium, and the like, may be used.
Normally, methanol conversion in zinc halides results in alkanes and alkenes, even when conducted in the presence of olefins, e.g. see U.S. applications Ser. No. 850,872 and 850,874 both filed on Nov. 14, 1977, as well as U.S. Pat. No. 4,059,647 issued Nov. 22, 1977. The particular advantage of this invention is that carboxylic acid esters are also produced. The highly branched ester products of the invention find use as solvents and chemical intermediates.